[Atrial synchronous ventricular stimulation with reduced a.v. delay time as a therapeutic principle in hypertrophic obstructive cardiomyopathy]

For the hypertrophic obstructive cardiomyopathy with left-ventricular pressure gradient in rest a causal therapy is nowadays not yet known. Therefore, it should be tested, in what respect from former observations over reductions of the pressure gradient by an untimely foreign excitation of the ventricles from the apex of the right ventricle a therapy principle can be derived. For this purpose out of a group of 84 patients by left-right heart catheterization, coronarography, computer cardio-tomography and scintigraphy of the myocardium 23 test persons with typical hypertrophic obstructive cardiomyopathy and a left-ventricular gradient in rest greater than or equal to 30 mm Hg were selected for the transitory electrostimulation. After placing of one electrode in the right atrium and another one in the right ventricle one after another a VOO-, VAT- and DOO-pacing were used. For the two last mentioned forms of stimulation as electronic atrio-ventricular retardation times 100, 40, 20, 10 and 5 ms were selected. With all three kinds of stimulation in 5 of the patients (group A) reductions of gradients greater than or equal to 51% and in 12 cases of hypertrophic obstructive cardiomyopathy (group B) diminishments between 30 and 50% could be obtained. Only in 6 patients (group C) reductions of less than or equal to 29% were registered. The optimum of prematurity necessary for obtaining maximum pressure reductions is individually different, but is almost in every case between 5 and 20 ms. Further seven parameters measured during the stimulation phases showed that these reductions are not caused by a decrease of the stroke volume, but by an enlargement of the effective opening of the outlet. Apparently, in a part of the patients with hypertrophic obstructive cardiomyopathy by the foreign excitation from the apex of the ventricle a temporary and spatial course of excitation can be induced, by means of which the degree of functional stenosing is decreased. Since for several patients the removal of the disturbance of the systolic function is to be regarded as therapeutically reasonable partial success, the transitory diagnostic pacing is recommended for all patients with typical hypertrophic obstructive cardiomyopathy and a gradient in rest greater than or equal to 30 mm Hg. The indications and technical prerequisites for a permanent electrostimulation with suitable systems are represented.